Most gas turbines have cooling air circulating, for example, through the inside of airfoils such as stator vanes. Such an airfoil has an airfoil air passage for circulating cooling air through the inside of the airfoil. A cylindrical body like an insert having a large number of holes is disposed inside this airfoil air passage to perform impingement cooling on airfoil walls with cooling air. The cooling air after impingement cooling is discharged into combustion gas through a plurality of cooling holes provided in the airfoil walls, and performs film cooling on the airfoil walls in the process.
This type of cylindrical body undergoes thermal elongation differently from the airfoil body. In such a case, therefore, a first end of two ends of the cylindrical body is fixed to the airfoil body by seal welding or brazing, while a second end is left free relative to elongation of the cylindrical body in a longitudinal direction. This allows the cylindrical body to absorb a difference in thermal elongation while maintaining a sealing effect between the airfoil body and the cylindrical body.
Patent Literature 1 describes a configuration for absorbing a difference in thermal elongation of an insert. According to Patent Literature 1, a free end of the insert is retained by a retaining member so that cooling air does not leak through a gap at the free end.